FAIR VALUE, Carrying Amounts and Estimated Fair Values of Other Financial Instruments (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Carrying Value [Member]
Financial assets [Abstract]
Net loans	$ 6,840,632	$ 6,231,837
Financial liabilities [Abstract]
Deposits	8,994,967	8,322,371
Overnight Federal Home Loan Bank borrowings	8,300	54,400
Securities sold under agreement to repurchase, short-term	241,708	259,367
Other Federal Home Loan Bank borrowings	3,750	1,976
Subordinated notes payable	13,795	0
Subordinated debt held by unconsolidated subsidiary trusts	77,320	97,939
Fair Value [Member]
Financial assets [Abstract]
Net loans	7,028,663	6,247,939
Financial liabilities [Abstract]
Deposits	8,997,551	8,308,765
Overnight Federal Home Loan Bank borrowings	8,300	54,400
Securities sold under agreement to repurchase, short-term	241,708	259,367
Other Federal Home Loan Bank borrowings	3,755	1,921
Subordinated notes payable	13,795	0
Subordinated debt held by unconsolidated subsidiary trusts	$ 77,320	$ 97,939